As far as I can determine, all editions of the Vatican Edition Kyriale (1905) and Graduale (1908) do not include a Credo V, Credo VI or Gloria ad lib. IV (Ambrosian).

By the 50s, in the Solesmes Liber Usualis/Graduale, these chants are included though, and the Graduale Simplex includes the Ambrosian Gloria, referenced as "ed. Vat. more Ambrosiano".

So—are these "unofficial" chants that Solesmes added (like the Du Mont ordinaries that appear in a few Libers), or were they approved later as "Vatican Edition", like the several newly composed propers after 1908 (Sacred Heart, Assumption, etc.)?

Thanks tomjaw, that is very interesting. I assume that is a Solesmes Gradual. Looking through ccwatershed's copies, I now see that the 1924 Liber Usualis has the same section "novissime approbati". And an accompaniment book from 1929 (Potiron) has these integrated in with the rest of the Kyriale.

But the 1953 Schwann Gradual doesn't. And most tellingly, the 1962 Missale Romanum, which has the intonations for every other Gloria and Credo, doesn't have the intonations for these.

So I think maybe they fall into the "approved, but not Vatican Edition" category, like the Solesmes variants of the peregrinus psalm tone and the Magnificat solemn tone I/VI mediant.

(Credo VII: The ICK website has a transcription they source to a 1927 Solesmes Gradual. Which makes sense together with tomjaw's 1924 (Solesmes?) Gradual already having V and VI.)